Used by author C. S. Lewis for a character in his 'Chronicles of Narnia' series, first appearing in 1950. Prince Caspian first appears in the fourth book, where he is the rightful king of Narnia driven into exile by his evil uncle Miraz. Lewis probably based the name on the Caspian Sea, which was named for the city of Qazvin, which was itself named for the ancient Cas tribe.